1. Field of the Invention
The invention relates to a process for heating fibrous paper material by providing a compact, high-consistency fibrous paper material, pulverizing the compact material into fibrous pulp friable material, disintegrating the fibrous pulp friable materials, and calefacting the fibrous pulp friable material.
2. Discussion of Background Information
Processes of the kind mentioned above are required, for example, as a preparation for the dispersing procedure of fibrous material, which is extracted from used paper. It is known that the characteristics of fibrous paper material can be significantly improved by dispersing or by a comparable mechanical/thermal treatment. In many cases, a fibrous pulp is used that has a dry content of between 15 and 35% and is brought to a temperature much above the ambient temperature. It is wise to arrange for a calefying, if the fibrous pulp already has the necessary consistency for dispersing. In this thickening process, a considerable part of the water already present in the fibrous pulp is expressed, wherein, first of all, its viscosity increases significantly, and second, less water must be heated. The thickening often proceeds in a worm press.
In a worm press, the fibrous pulp suspension is pressed between a conveyer screw and perforated jacket surrounding the conveyer screw, so that the water escapes through the jacket. The pressed object or plug is pushed out of the worm and breaks up into pieces. The pieces can easily be heated to the targeted temperature, but a relatively long calefaction period is required. By pulverizing these pieces, the calefaction period can be shortened, for example in a tearing worm or in a system with counter-rotating rotors, but that is very expensive.
Prior to the present invention, relatively long periods of calefaction, many minutes, for example, were accepted as a fact, especially when a high temperature over 90.degree. C. was desired.